Quantitative detection of potassium chloride solutions at different concentrations using terahertz waves

Terahertz detection, utilizing electromagnetic waves within the terahertz spectral band, offers a sophisticated approach for the analysis and identification of materials. This technique capitalizes on the distinctive resonant interactions between terahertz waves and the vibrational modes of various non-polar substances and biochemical entities. A notable challenge arises in the terahertz time-domain spectroscopy (THz-TDS) when applied to water-rich samples, owing to the significant absorption characteristics of water molecules at these frequencies. Although various methodologies exist for the detection of potassium chloride, a common substance with extensive applications, its analysis using THz-TDS, particularly in aqueous solutions, remains unexplored in literature. This investigation delineates the terahertz spectral behavior of potassium chloride in powdered form and extends to evaluate aqueous solutions with concentrations ranging from 3 to 60 mmol/L. The findings indicate a pronounced absorption peak within the terahertz range for potassium chloride solutions, which progressively lowers in intensity as the concentration increases. Consequently, THz-TDS emerges as a swift, precise, non-invasive, and safe modality for the quantification of potassium chloride in solutions.